Influences originating from the upper airway on control of breathing will be studied. Special emphasis will be given to an upper airway pressure reflex. Several aspects of this reflex response will be studied using an isolated upper airway preparation in tracheostomized, anesthetized animals. Specificity of this reflex response will be tested by determining the effects of upper airway pressure changes on the respiratory activity of various upper airway muscles. Species variability and maturational effects of the reflex response will also be investigated. Effects of upper airway pressure changes on inspiratory and expiratory duration as well as the effect on peak diaphragmatic activity will be studied in detail. Additionally, laryngeal mechanoreceptors responding to upper airway pressure changes will be identified, localized and their responses documented. Action potentials from the single fibers of the peripheral cut end of the internal branch of superior laryngeal nerve will be recorded for this purpose. The above studies are anticipated to provide valuable insight into maintenance of upper airway patency as well as the contribution of upper airway in the control of breathing. In addition, these studies are viewed as relevant to our understanding of apnea seen in a variety of clinical states such as apnea of prematurity, SIDS and sleep apnea.